1. Field of the Invention
This invention relates to a backpack used to carry a load on the back of a wearer, and more particularly, to a backpack having an enclosed envelope including a front wall positionable against the wearer's back and a compressively stressed internal frame disposed within the envelope tensioning the front wall.
2. Description of the Prior Art
Backpacks have been used for many years to assist humans in transporting loads on their backs. Backpacks have included sacks having one or more compartments for the stowage of various articles, and often a frame has been provided to add strength and rigidity to the sack as it is held in position on the back of the wearer by shoulder straps or the like.
One such pack shown in U.S. Pat. No. 2,421,244 includes a frame having a pair of upright side rails and a plurality of arcuate cross frame members interconnected in a vertically spaced arrangement. The length of the cross members decreases from bottom to top causing the frame to taper inwardly. A like tapered fabric sheet is provided over the frame and is open at the bottom.
U.S. Pat. No. 3,860,157 discloses a backpack having a readily disassembled frame which is held together by netting wrapped around the upright side frame members.
In addition to the above described prior art, U.S. Pat. No. 3,734,366, granted May 22, 1973 and pending patent application Ser. No. 588,795, filed June 20, 1975, disclose backpacks employing a lightweight pack frame constructed of rigid polyvinyl chloride or the like.